From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Stancek Date: Tue, 23 May 2017 05:45:13 -0400 (EDT) Subject: [LTP] [PATCH v2] [RFC] pselect01: Tune thresholds In-Reply-To: <20170523091608.GA18460@rei.lan> References: <20170512141658.26810-1-chrubis@suse.cz> <20170515131329.GA12586@rei.suse.de> <1308561590.18511159.1495442352952.JavaMail.zimbra@redhat.com> <20170522131944.GC11771@rei.lan> <297220533.19197153.1495465050258.JavaMail.zimbra@redhat.com> <20170522151555.GD11771@rei.lan> <24535361.19636257.1495526084444.JavaMail.zimbra@redhat.com> <20170523091608.GA18460@rei.lan> Message-ID: <833996051.19688092.1495532713977.JavaMail.zimbra@redhat.com> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: ltp@lists.linux.it ----- Original Message ----- > Hi! > > > Hmm, strange, it looks like for 100us we got more or less all samples > > > close to 160us but for 500us half of the samples are close to 560us and > > > about 400 is more than 1000us, that does not look right. I wonder what > > > happens there. And the same for the rest of the measurements everything > > > but 100us sleeps has two peaks that are more or less 500us apart. So far > > > my machines, even VMs, had one peak and some outliners. > > > > > > Can you try to rerun the test with a realtime priority? > > > > Ran as "chrt -f 50 ./measure", results attached. > > > > Looks more or less the same and I still cannot reproduce the issue on > any of the machines I have here. > > Looking at errata for AMD cpus #778 says that TSC may drift under some > circumstances: > http://support.amd.com/TechDocs/51810_16h_00h-0Fh_Rev_Guide.pdf#unique_29 > > Can you try to disable P-state in BIOS or set cpufreq to performance? Not sure if I can get easily to BIOS, it's a system in remote location. As for cpufreq, it already was set to performance: # cat /sys/devices/system/cpu/cpufreq/policy*/scaling_governor performance performance performance performance Regards, Jan